Many current vaccines against microbial pathogens comprise live attenuated or non-virulent strains of the causative microorganisms. Many vaccines comprise killed or otherwise inactivated microorganisms. Other vaccines utilize purified components of pathogen lysates, such as surface carbohydrates or recombinant pathogen-derived proteins. Vaccines that utilize live attenuated or inactivated pathogens typically yield a vigorous immune response, but their use has limitations. For example, live vaccine strains can sometimes cause infectious pathologies, especially when administered to immune-compromised recipients. Moreover, many pathogens, particularly viruses, undergo continuous rapid mutations in their genome, which allow them to escape immune responses to antigenically distinct vaccine strains.
Given the difficulty of vaccine development, many vaccines are in extremely short supply. For example, as of October 2007, there are influenza, varicella, and hepatitis A vaccine shortages in the United States. In some instances, vaccine shortages occur because not enough manufacturers devote their facilities to vaccine production to keep up with demand. In some cases, vaccine shortages are attributed to low potency of the vaccine, which means a large amount of vaccine product must be administered to each individual in order to achieve a prophylactic effect. For example, some vaccines cannot be administered as an intact organism (even if attenuated or killed) because they cause infectious pathologies. Instead, such vaccines usually comprise purified pathogen components, which typically leads to a much less potent immune response.
Thus, there is a need in the art for systems and methods for producing highly immunogenic, effective vaccines. There is also a need for improved vaccine compositions that can potently induce long-lasting immune responses. For the treatment and prevention of infectious diseases, there is a need for improved vaccine compositions that are highly immunogenic but do not cause disease.
Smoking of cigarettes, cigars, and pipes is a prevalent problem in the United States and worldwide. Smoking tobacco and smokeless tobacco are rich in nicotine, which is a known addictive substance. Peak levels of nicotine in the blood, about 25 to 50 nanograms/ml, are achieved within 10-15 minutes of smoking a cigarette. In humans, smoking a cigarette results in arterial nicotine concentrations being 10-fold higher than venous nicotine concentrations because nicotine is rapidly delivered from the lungs to the heart (see Henningfield (1993) Drug Alcohol Depend. 33:23-29). This results in a rapid delivery of high arterial concentrations of nicotine to the brain. Once nicotine crosses the blood-brain barrier, evidence suggests that it binds to cholinergic receptors. When nicotine binds to these receptors, it can affect normal brain function, by triggering the release of other neurotransmitters, such as dopamine. Dopamine is found in the brain in regions involved in emotion, motivation, and feelings of pleasure. It is the release of neurotransmitters, especially dopamine, that is responsible for the tobacco user's addiction to nicotine or other intake of nicotine.
Nicotine is an alkaloid derived from the tobacco plant that is responsible for smoking's psychoactive and addictive effects. Nicotine is formed of two rings linked together by a single bond: an aromatic six-membered ring (pyridine) and an aliphatic five-membered ring (pyrrolidine). The pyrrolidine is N-methylated and linked through its carbon-2 to the carbon-3 of pyridine. Thus, the carbon-2 is chiral, and there is virtually free rotation around the single bond linking the two rings. It has been established that the absolute configuration of carbon-2 is S. Thus, the natural configuration of nicotine is (S)-(−)-nicotine.
Therapies for nicotine addiction have been developed, but are largely ineffective. The two most popular therapies remain the nicotine transdermal patch and nicotine incorporated into chewing gum. These therapies, termed “nicotine replacement therapies” (NRTs), replace the amount of nicotine which the user previously received from smoking and act to wean the user off nicotine. However, certain drawbacks are seen with this type of therapy. Particularly, there is low penetration of nicotine into the bloodstream and therefore an increased desire to smoke.
There remains a need in the art to develop improved methods of treating addiction (such as addictions to nicotine, cocaine, heroine, alcohol, and other drugs). Ideal methods for treating addiction would, for example, result in minimal withdrawal symptoms, encourage patient compliance by being simple to administer, and result in low relapse rates among patients.